Several computer systems are presently available for capturing motion video information as a computer data file including data representative of a sequence of several digital still images. Such digitized data is often compressed, using common compression standards such as MPEG (Motion Picture Experts Group) and motion-JPEG (Joint Photographers Expert Group) compression.
One difficulty to overcome in video capture is that there are several formats in which video information may be received. These include square and nonsquare pixel formats from NTSC and PAL format video. Prior capture systems generally are designed such that prior knowledge of the video pixel data format is required.
Another difficulty to overcome in video capture is achieving a high compression ratio while maintaining good image quality upon decompression. Image quality is often inversely related to the compression ratio. The compression ratio also affects memory and bandwidth requirements. Achieving a low cost video capture circuit often involves reducing the amount of memory needed for the capture circuitry, as well as the size and complexity of the circuit.
A difficulty to overcome in video playback is that there are several formats in which motion video information may be needed. For example, motion video information may be stored in a different form of computer data file, requiring conversion, for example, from Motion-JPEG to MPEG. Or, motion video information be encoded as a synchronized television signal for recording on a video tape.
Motion video information may also need to be processed to add effects in an editing process, such as transition effects and titles. Such manipulation may require the steps of decompression of the video information, addition of the effect and compression of the resulting video information. These steps result in increased complexity because of a data flow path both to and from the compression/decompression circuitry.
Low cost video circuitry that is suitable for home use by a nonprofessional still should provide basic processing operations for capture, playback and manipulation of motion video information. Accordingly a general aim of the present invention is to provide a video processing circuit for connection to a computer which provides such functionality and which is capable of handling several data formats. Another general aim of the present invention is to provide a video capture circuit which can be connected to a standard bus interface such as a peripheral component interconnect (PCI) bus.